This invention relates generally to digital communication systems. In particular, this invention relates to transmission of both power and data over a common wire.
In many applications, space constraints encourage minimization and simplification of wiring. One such application (although this invention is not limited to such) is within a video game machine. In many video games, such as those gaming machines used in arcades and casinos, the video screen is carried by a hinged surface.
A door carrying a display is movable between open and closed positions, typically in hinged fashion. The door is opened quite frequently in cases of repairs, money retrieval from a cash box, or maintenance, in order to gain access to the working parts of the machine.
A gaming controller is located inside a interiorly of the display unit, the controller providing or generating game play information for display by the display. In some cases, the game can comprise a symbol displaying device and a game machine using the same in which rotational members having predetermined symbols (mark, numeral, letter, pattern and so forth) are rotated in different directions. In this game machine, existence and kind of winning are determined in accordance with a combination of the symbols which is displayed when the rotational members are stopped.
In this electrical engineering environment, several components of the game must act in concert. The manual input (e.g., pulling on a lever of a slot machine, pushing a button to make play) is a peripheral device. The input must be coupled with a controller, which must be coupled with a display. Other peripherals could include a receipt printer, a currency validator, gaming lights, security, and audio/visual components. All are typically powered, and the electrical controls are located inside the hinged portion of the gaming unit. A large amount of wiring exists inside of these machines, to communicate both data between the peripherals and control unit, and to communicate power to all of the components requiring power (most in modern video gaming).
Many forms of digital communications used today require a first set of wires to carry the digital messages (data) from one place to another; and another set of wires to carry power from a power source to the power usage station. External power supply is carried to “loads.” An electrical load is an electrical component or portion of a circuit that consumes electric power. This is opposed to a power source, such as a battery or generator, which produces power. In electric power circuits examples of loads are appliances and lights. The term may also refer to the power consumed by a circuit.
When system uses dedicated wires for communications, those wires are often referred to collectively as the “communications bus.” A communications bus refers to a group of wires whose responsibility it is to get information from the source to the intended receiver or from the receiver to the source. Those wires are acting as a stand-alone sub-system and must be isolated from other sub-systems. In more complex systems it is possible to have several communications buses. This would become necessary if the different communications sub-systems were incompatible and the digital information being conveyed by one sub-system would interfere with the operation of another sub-system.
Synchronous Serial interface (SSI) is a widely used serial interface standard for industrial applications between a controller and a sensor. Data is sent bit by bit over wires between the controller (master) and sensor (peripheral). The SSI bus normally consists of just two signals, data and clock, and communicates in one direction. This called half duplex or simplex communication.
Serial Peripheral Interface (SPI) is a synchronous serial communication interface specification used for short distance communication between a microcontroller and a peripheral. SPI uses separate lines for data and a clock to maintain registration between data sent and data received. The clock signals the receiver to sample bits on the data line. SPI devices use a master to control a peripheral. A SPI bus is defined as being full duplex, as it contains provisions for communicating in both directions. However, SPI communication is sometimes only implemented as half duplex. A SPI bus frequently uses four signals, data out, data in, clock, and a device select line.
In the prior art, an external power supply sends power to a controller circuit board over power lines. The external supply also sends power to the peripheral circuit board, again over power lines. A different set of lines—data lines, run between the controller circuit board and the peripheral circuit board to send commands from the controller circuit board to the peripheral circuit board, and to receive data back from the peripherals to the controller.
In another prior art system as specified by IEEE 802.3, Power over Ethernet (PoE) can be supplied. In a PoE system, power and data are communicated through Ethernet cabling. An example of PoE is single cable to provide both a data connection and electrical power to devices such as wireless access points.